Zirconia based blades and foils for razors and a method for producing same

ABSTRACT

Stabilized or partially stabilized zirconia paste may be screen printed onto hydrophilic plastic film in the form of a mesh. On firing, this becomes a very sharp foil for electric razors with excellent wear and flexibility characteristics. Stabilized or partially stabilized zirconia may also be screen printed onto a wettable plastic film then fired to produce low cost razor blades with an excellent edge. A curved razor blade incorporating an array of holes, each of which has a knife edge periphery, offers greater cutting power and control of the skin surface than a single or double edge.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is entitled to the benefit of and incorporates byreference essential subject matter disclosed in InternationalApplication No. PCT/US2003/030958 filed on Oct. 1, 2003 and BritishProvisional Application No. 0222712.2 filed on Oct. 1, 2002, BritishProvisional Application No. 0223567.9 filed on Oct. 10, 2002, andBritish Provisional Application No. 0223882.2 filed on Oct. 16, 2002,the disclosures of which are incorporated by reference herein in theirentirety.

FIELD OF THE INVENTION

This invention relates generally to blades and foils for razors, andmore particularly relates to zirconia based blades and foils for razors,as well as methods for producing same.

BACKGROUND OF THE INVENTION

Electric razors with cutting foils and wet shave razors with cuttingblades have been in use for many decades. With respect to electricrazors, they comprise a pierced foil and cutter. The foil is generallyelectroformed from nickel, which provides a very sharp edge but oflimited hardness. Electric razor foils are generally made byelectroforming nickel. This is a relatively expensive process and thehardness of the resulting nickel cutting edges is not that high.

With respect to wet shave razors, the razor blades traditionally have astraight cutting edge that extends the length of the razor head. Safetyrazors have guards to control the position of the skin with respect tothe cutting edge, so that the cutting edge rides over the skin but cutsprotruding hair. Such razor blades have traditionally been made fromhigh quality carbon steel. The innovation of using stainless steel hasbeen fraught with the difficulty of forming and holding an ultra sharpedge. Ground ceramic razor blades tend to have a ragged microstructurerather than rounded, and consequently dig into skin rather than slidingover it.

Accordingly, it is a general object of the present invention to providezirconia based blades and foils, and methods of fabrication thereof,that overcome the above-identified drawbacks of prior razors.

SUMMARY OF THE INVENTION

The present invention resides in a method of fabricating a foil for anelectric razor. A substrate is provided including a combustible surface.A foil plan form is generated on the combustible surface with a zirconiabased ink such that flow of the ink under surface tension forcesgenerates sharp edges to the foil. The foil plan form is fired to burnaway the combustible surface such that zirconia forms a durable foilthat maintains sharpness over repeated use. The zirconia based ink caninclude partially stabilized or fully stabilized zirconia. The printingof the foil plan form can be accomplished by either screen printing orvacuum forming. The combustible surface can include, for example, aplastic film of high surface finish, and is preferably hydrophilic.

The present invention also resides in a method of fabricating a bladefor a wet shave razor. A substrate is provided including a combustiblesurface. A zirconia based ink is generated on the combustible surfacesuch that the ink wets the substrate and edges of the ink slightly toform a plurality of sharply pointed meniscus to serve as cuttingsurfaces. The ink is fired to burn away the combustible surface and toharden a rounded, sharp edge on the plurality of meniscus. Preferably,the sharp edges of the meniscus have an edge radius of about 50nanometers or less.

The present invention further resides in a blade for a wet shave razorthat is bidirectional and comprises a substrate curved along a directionof blade movement to conform to a contour of the skin of a user. Theblade substrate defines a plurality of holes each having a periphery. Aleading portion of the holes in the direction of blade movement servesas a guard, and a trailing portion of the holes serves as a cuttingedge. Preferably, the substrate includes partially stabilized or fullystabilized zirconia. The holes are arranged in an array that can beeither even or staggered. The shape of the holes can be, for example,rectangular or diamond-shaped.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a top plan view of a razor blade substrate defining an arrayof rectangular slots serving as cutting edges in accordance with thepresent invention.

FIG. 1B is a top plan view of a razor blade substrate defining an arrayof staggered rectangular slots serving as cutting edges in accordancewith another embodiment of the present invention.

FIG. 1C is a top plan view of a razor blade substrate defining an arrayof diamond-shaped slots serving as cutting edges in accordance with afurther embodiment of the present invention.

FIG. 2 is an elevational, cross-sectional view of the razor blade ofFIG. 1 showing a curved contour of the blade in contact with the skin ofa user.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, an electric razor foil can bemade from zirconia ceramic. The zirconia may be partially or fullystabilized. The foil may be fabricated by screen printing the foil planform onto a hydrophilic surface with a zirconia based ink, such thatflow of the ink under surface tension forces generates very sharp edgesto the ceramic foil. The planar hydrophilic surface may be combustibleso that it vanishes during firing. The surface is preferably a plasticfilm of good surface finish. The foil network may be biaxiallyextensible to conform to the skin. The cutter may also be in the form ofa zirconia foil. The zirconia print and plastic film may be formed priorto firing. Vacuum forming may be appropriate. Appropriate binders andplasticisers in the zirconia ink may stop cracking of the ceramic printduring the forming process.

Partially stabilized zirconia has the hardness and toughness of toolsteel. It has excellent wear characteristics and takes a very keen edge.While it is much more expensive, the quantity in a razor foil is minimaland it may be fabricated more cheaply than electroforming.

A razor foil pattern may be precisely screen printed onto a plastic filmwith a zirconia ink. If the film is slightly hydrophilic it may bearranged, by controlling the ink properties, such that the edges of theprint may run slightly under the influence of surface tension forces toprovide an extremely sharp edge. Even a low cost plastic film may have asurface finish approaching optical quality and the zirconia print willaccurately reproduce this.

The printed plastic film may be fired in the conventional manner. Theplastic will burn away at a low temperature and the zirconia will form avery thin foil of extreme toughness. It will maintain its sharpness fora long time.

The foil pattern can be printed in a manner that permits biaxialextension to follow the contours of the skin. A cutter in foil form canalso be fabricated which will follow the outer foil and provide aflexible cutting surface.

The printed plastic may be vacuum formed if desired. This permits theforming of the profiled cutters used in current multi head shavers. Theform may also be exploited to assist with maintaining dimensionalstability during the firing process.

Further in accordance with the present invention, razor blades can befabricated from a ceramic ink that is screen printed on a combustiblesurface and then fired. The ceramic is preferably stabilized orpartially stabilized zirconia. The combustible surface is preferably aplastic film of high surface finish. The ink vehicle and combustiblesurface may be so chosen that the ink wets the combustible surface.

Stabilized zirconia forms exceptional cutting blades. It is extremelystrong, tough and hard. In thin sheets it may be very pliable. It hasbeen discovered to be an excellent medium for razor blade fabrication.The raw material is very expensive compared with steel and is expensiveto diamond machine. Cutting edges in zirconia are conventionally createdby diamond machining, but this process produces ragged edges on amicro-scale which tend to dig into skin rather than slide over it. This,of course, is disastrous in a razor blade.

Screen printing of ceramic inks is a well known mass productiontechnique in hybrid electronics. This produces a thin film of veryfinely controlled thickness at very low cost. The ink comprises veryfinely powdered ceramic in a binder and solvent. It is possible tochoose the composition of ink such that it wets the substrate and theedges of the print flow slightly to form a sharply pointed meniscus. Onfiring, the substrate may burn away and the meniscus will form a verysharp edge. The firing process causes the finely powdered grains tosinter into a solid mass. This process may be exploited to form an edgeto the blade which is rounded on a microscale. With modern millingtechniques, the powder particle size may be some tens of nanometers. Itis therefore possible to organize the firing to produce a blade with anedge radius of about 50 nanometers or less.

The ceramic will take the surface finish of the substrate on the printedside, which may approach optical quality for many plastic films. If thisis the side that faces the skin, a very smooth blade will result. Screenprinting produces very thin layers with excellent reproducibility.Zirconia blades as thin as about 0.025 mm are feasible. By using thinblades of minimum width, blade costs of a fraction of a penny arefeasible.

This fabrication technique offers the advantages of large scale masscoupled with low materials cost and no finishing processes.

Further in accordance with the present invention, a metallic or ceramicrazor blade can be curved and define a plurality of holes or slots, someor all of which incorporate a cutting edge as part or all of theirperiphery. With reference to FIG. 1A, for example, a razor blade isindicated generally by the reference number 10. The blade 10 defines aplurality of holes or rectangular slots 12 that preferably form anarray. As shown in FIG. 1A, the array of slots 12 includes five columns14, 16, 18, 20 and 22. However, the array can include a fewer or greaternumber of columns than that illustrated without departing from the scopeof the present invention. A portion of the periphery of the slots 12serve as cutting edges that are well protected within the slots. As aresult, the edge of the blade is no longer in need of carefulprotection.

With respect to the direction of blade movement during a shavingoperation as indicated by the arrow A, the longer edges of therectangular slots 12 are trailing edges 24 and leading edges 26. Theblade 10 further defines interconnecting spokes 28 between shorter edges30 of the rectangular slots 12 for enhancing the rigidity of the blade.A periphery 32 of the blade 10 may be used to retain the blade in arazor.

The leading edges 26 serve as a guard, and the trailing edges 24 serveas the cutting edge. However, the blade 10 can be used in a directionopposite to that indicated by the arrow A. When used in such oppositedirection, the edges 24 are the leading edges serving as the guard, andthe edges 26 are the trailing edges serving as the cutting edges.

Turning to FIG. 1B, a blade in accordance with another embodiment of thepresent invention is indicated generally by the reference number 110.Like elements with those shown in FIG. 1A are indicated by likereference numbers preceded by “1”. The blade 110 defines a plurality ofholes or staggered rectangular slots 112 that form an array. As shown inFIG. 1B, the array of slots 112 includes five columns 114, 116, 118, 120and 122. The slots in adjacent columns are positioned in staggeredrelationship to one another to provide a consistent cutting surfacealong a direction of the blade transverse to that of the direction ofmovement.

Similar to the previous embodiment, a portion of the periphery of theslots 112 serve as cutting edges. With respect to the direction of blademovement during a shaving operation as indicated by the arrow A, thelonger edges of the rectangular slots 112 are trailing edges 124 andleading edges 126. The blade 110 further defines interconnecting spokes128 between shorter edges 130 of the rectangular slots 112 for enhancingthe rigidity of the blade. A periphery 132 of the blade 110 may be usedto retain the blade in a razor.

The leading edges 126 serve as a guard, and the trailing edges 124 serveas the cutting edge. However, the blade 110 can be used in a directionopposite to that indicated by the arrow A. When used in such oppositedirection, the edges 124 are the leading edges serving as the guard, andthe edges 126 are the trailing edges serving as the cutting edges.

Turning to FIG. 1C, a blade in accordance with a further embodiment ofthe present invention is indicated generally by the reference number210. Like elements with those shown in the previous embodiments areindicated by like reference numbers preceded by “2”. The blade 210defines a plurality of holes or staggered diamond-shaped slots 212 thatform an array. The blade 210 also preferably defines partial orhalf-diamond-shaped slots 213 at ends of the array for even distributionof cutting surfaces between sides of the blade. As shown in FIG. 1C, thearray of slots 212 includes five columns 214, 216, 218, 220 and 222. Theslots in adjacent columns are positioned in staggered relationship toone another to provide a consistent cutting surface along a direction ofthe blade transverse to that of the direction of movement.

Similar to the previous embodiments, portions of the periphery of theslots 212 serve as cutting edges. With respect to the direction of blademovement during a shaving operation as indicated by the arrow A, thediamond-shaped slots 212 each include trailing edges 224, 225 andleading edges 226, 227. A periphery 232 of the blade 210 may be used toretain the blade in a razor.

The leading edges 226, 227 serve as a guard, and the trailing edges 224,225 serve as the cutting edge. However, the blade 210 can be used in adirection opposite to that indicated by the arrow A. When used in suchopposite direction, the edges 224, 225 are the leading edges serving asthe guard, and the edges 226, 227 are the trailing edges serving as thecutting edges.

With reference to FIG. 2, a blade in accordance with the presentinvention may have an overall curvature to expose different angles ofblade to the skin. A curved blade 310 defines an array of holes or slots312 in contact with skin 313 of a user during a shaving operation. Asshown in FIG. 2, the array of slots 312 includes five columns 314, 316,318, 320 and 322. With respect to the direction of blade movement duringa shaving operation as indicated by the arrow A, a hair 323 is shownbeing cut by a trailing or cutting edge 324 of one of the holes 312. Thecurvature and flexibility of the blade 310 may be predetermined to offerthe maximum ability to follow skin contours. Several cutting edges 324may be in contact with the skin simultaneously. The leading edges 326 ofthe holes or slots 312 control the access of the skin 313 to the cuttingedges 324 of the hole 312. The blade may be formed from metal byelectroforming or by grinding away dimples in a planar shim. The blademay also be formed by screen printing ceramic ink as an array of holes,and then firing the print. The rheology of the ink may be arranged sothat the flow of the periphery of the wet print may form a meniscuswhich becomes a polished razor edge on firing. The ceramic is preferablypartially stabilized or fully stabilized zirconia ceramic. The ceramicmay also be ground and polished after firing if desired.

Razor blades traditionally have a straight cutting edge. An array ofholes 25 with cutting edges around their periphery in accordance withthe present invention provides a longer cutting edge per squaremillimeter of blade and a tighter control of the angle at which the skinmeets the blade. This results in a more rapid and closer shave with lesschance of nicking the skin.

In a metal blade, such an array may be made by electroforming.Electroforming is relatively expensive for disposable blades, however,and nickel, which is the only practical metal for this technique, is notexceptionally hard. An alternative is to form an array of indentationsin a planar metal shim, and then to grind away the raised bumps tocreate holes surrounded by a cutting edge.

A better process is to screen print the blade pattern with partiallystabilized zirconia ink. If the rheology of the ink and the nature ofthe substrate are carefully chosen, the edges of the print flow tocreate a wetting meniscus. On firing, this meniscus naturally creates apolished razor edge.

As will be recognized by those of ordinary skill in the pertinent art,numerous modifications and substitutions may be made to theabove-described embodiment of the present invention without departingfrom the scope of the invention. Accordingly, the preceding portion ofthis specification is to be taken in an illustrative, as opposed to alimiting sense.

1. A method of fabricating a foil for an electric razor, comprising thesteps of: providing a substrate including a combustible surface;generating a foil plan form onto the combustible surface with a zirconiabased ink such that flow of the ink under surface tension forcesgenerates sharp edges to the foil; and firing the foil plan form to burnaway the combustible surface such that zirconia forms a durable foilthat maintains sharpness over repeated use.
 2. A method as defined inclaim 1, wherein the step of generating includes screen printing thefoil plan form onto the combustible surface.
 3. A method as defined inclaim 1, wherein the step of generating includes vacuum forming the foilplan form onto the combustible surface.
 4. A method as defined in claim1, wherein the zirconia based ink includes partially stabilizedzirconia.
 5. A method as defined in claim 1, wherein the zirconia basedink includes filly stabilized zirconia.
 6. A method as defined in claim1, wherein the combustible surface is hydrophilic.
 7. A method asdefined in claim 1, wherein the combustible surface is a plastic film ofhigh surface finish.
 8. A method of fabricating a blade for a wet shaverazor, comprising the steps of: providing a substrate including acombustible surface; generating a zirconia based ink onto thecombustible surface such that the ink wets the substrate and edges ofthe surface slightly to form plurality of sharply pointed meniscus toserve as cutting surfaces; and firing the ink to burn away thecombustible surface and to harden a rounded, sharp edge on the pluralityof meniscus.
 9. A method as defined in claim 8, wherein the step ofgenerating includes screen printing the zirconia based ink onto thecombustible surface.
 10. A method as defined in claim 8, wherein thezirconia based ink includes partially stabilized zirconia.
 11. A methodas defined in claim 8, wherein the zirconia based ink includes fullystabilized zirconia.
 12. A method as defined in claim 8, wherein thecombustible surface is hydrophilic.
 13. A method as defined in claim 8,wherein the combustible surface is a plastic film of high surfacefinish.
 14. A method as defined in claim 8, wherein the sharp edges ofthe meniscus have an edge radius of about 50 nanometers or less.